Trench type MOSFETs and IGBTs are MOSGATED devices I which a conductive gate polysilicon is forme3d in spaced parallel trenches. Such devices and processes for their manufacture are shown in copending application Ser. No. 10/981,114, filed Nov. 4, 2004 in the names of Cao et al. entitled TRENCH POWER MOSFET WITH REDUCED GATE RESISTANCE (IR-2582), published as U.S. patent application Publication Number 2005/0112823 A1 and issued as U.S. Pat. No. 7,368,353, which is hereby incorporated in its entirety by reference. Such devices have an excellent low RDSON, useful in switching applications.
It is desirable to further improve the switching performance of such devices by improving (reducing) the gate to drain capacitance and eliminating or reducing the possible initiation of parasitic bipolar action. It is also desirable to provide resistance to single event gate rupture and single event breakdown for devices exposed to external particle radiation as exists at high altitude or in space applications while maintaining the low conduction losses of the trench device.